60 GHz transmission systems are particularly well suited to the transmission of data at high bit rates on short distances. For example, a transmission system of this kind is well suited to connectivity between different elements of a home cinema. Indeed, in this case of use, the range of transmission is limited to about ten meters but the bit rates brought into play are very high, sometimes more than one gigabit per second owing to the nature (both video and audio) of the high resolution of the information transmitted.
Transmission systems of this kind require perfect synchronization between the transmitters and the receivers, especially in a system for broadcasting an audio content with multiple channels, comprising up to ten (or more) speakers known as a “surround sound system”.
Indeed, in this specific case, a transmitter (comprising also an audio decoder) transmits in a perfectly synchronous way on different audio channels coming from a single source to a set of receivers, each comprising one speaker and all these receivers have to restore the sound totally with perfect synchronization in order to give the sound an effect of spatialization.
Given the random behavior of the transmission channel of such transmission systems (which in particular are highly sensitive to the shadowing caused for example by an individual going through the field of transmission), it is necessary to make multiple transmissions of data in order to ensure efficient reception of this data beyond a predefined residual error rate.
Error correction techniques are conventionally implemented in the digital data-processing systems of the different devices (transmitters and/or receivers) of the transmission systems to optimize the use of the transmission channel (i.e. to obtain a maximum capacity of transport of the transmission channel) but also to increase the reliability of the data received.
For example, first classic error correction techniques are MIMO (“Multiple-Input Multiple-Output”) techniques relying on spatial diversity. In particular, these MIMO type error correction techniques use multiple transmission and reception of same data symbols to improve the estimation of these data symbols at reception.
MIMO type techniques rely on good a priori knowledge of the characteristics of the transmission channel despite its random behavior which varies in the course of time, the correlation between the data symbols transmitted several times and those received several times relying on this a priori knowledge of the transmission channel.
Consequently, one drawback of these first MIMO error correction techniques is that they are not suited to remaining efficient during the occurrence of an unexpected modification (modification outside the framework of the characteristics of the transmission channel defined a priori) of the transmission conditions (for example the appearance of an obstacle on the transmission path causing a shadowing on the transmission path) in the communications network.
Furthermore, another drawback of these first techniques is that they rely on the reduction of the error rate in the data symbols received rather then the correction of errors within these same symbols.
Second prior art error correction techniques analyze the quality of a received signal (for example through the measurement of the signal-to-noise ratio or SNR) to select the received piece of data having the best reception quality before decoding it.
Again, one drawback of these second error correction techniques relies on the fact that it cannot be used to pursue an efficient error correction process when there is an unexpected deterioration (caused for example by the appearance of an obstacle on the transmission path causing a shadowing on the transmission path) of the conditions of transmission in the network.